A plasma reactor for processing a workpiece can employ an electron beam as a plasma source. Such a plasma reactor can exhibit non-uniform distribution of processing results (e.g., distribution of etch rate across the surface of a workpiece) due to non-uniform distribution of electron density and/or kinetic energy within the electron beam. Such non-uniformities can be distributed along the direction of beam propagation and can also be distributed in a direction transverse to the beam propagation direction.